1. Field of the Invention
The present invention relates to a touch panel and, more particularly, to a piezoresistive device for generating a signal using the piezoresistive property of a carbon nanotube, a method of manufacturing the piezoresistive device and a piezoresistive-type touch panel having the piezoresistive device.
2. Background Art
A touch panel is an input device used in electronic devices such as computers, personal digital assistants and various kinds of office equipment. The touch panel enables a user to input signals by a touch using a finger or a stylus without having to use an intermediate input device such as a keyboard or a mouse.
Depending on the configuration method, the touch panel is divided into a resistive touch panel, a capacitive touch panel, a surface acoustic wave (SAW) touch panel, an infrared touch panel, and so forth.
The resistive touch panel is composed of two overlapping substrates coated with transparent electrodes. If upper and lower electrode layers are brought into contact with each other by the pressure applied with a finger or a stylus, an electric signal is generated to indicate a touch position. The resistive touch panel is inexpensive, highly accurate and advantageous in size reduction. However, a difficulty is encountered in manufacturing a strong enough resistive touch panel because a touch is recognized only when two substrates make physical contact with each other.
The capacitive touch panel is driven by static electricity generated in a human body. The capacitive touch panel is highly durable, short in response time and superior in transmissibility. However, the capacitive touch panel is quite expensive and cannot be operated with a stylus or a gloved hand.
The surface acoustic wave touch panel is designed to detect a decrease in the amplitude of ultrasonic waves when the ultrasonic waves meet an obstacle. The surface acoustic wave touch panel is superior in light transmittance but vulnerable to contamination and liquid attack.
The infrared touch panel makes use of the property of infrared rays which are invisible to the human eyes and are interrupted by an obstacle due to their tendency to go straight. The infrared touch panel includes light emitting elements and light receiving elements, both of which are arranged in a mutually opposing relationship. The infrared touch panel recognizes the coordinates where the infrared rays are interrupted by a touch. The infrared touch panel does not require the use of an ITO film and can be configured by a single sheet of glass, thus exhibiting superior transmittance.
Among the various kinds of touch panels mentioned above, the resistive touch panel and the capacitive touch panel are extensively used in recent years. However, the resistive touch panel suffers from a problem in that the electrodes thereof may be destroyed by a touch. The capacitive touch panel poses a problem in that it cannot be operated with a non-human-body tool.